When you are trying to delete a verified domain name in Office 365, an error comes saying that some users or Office365 services are still attached to the domain.
How to Solve?
- Make sure that no users are associated with the domain that you are trying to delete. Verify this by going into Users And Groups, and Edit a user. Confirm that the domain you are trying to remove, example microsoft.com, is not listed.
- No security groups/distribution groups have the accounts attached to microsoft.com. Security groups/distribution groups can be access by login to Office 365, click on Users And Groups, and select Security Groups.
- If you have just deleted the users, or changed the domain for each individual users, you will need to wait for a while as it need to sync the changes to the different Office365 service settings.
- If the accounts are uploaded to Dirsync, you need to stop the Dirsync synchronization to change the accounts to a Cloud Only account. Then, you need to do above steps to delete the Security groups or manually modify the e-mail addresses in Office 365, Exchange Online.